A technique of formation of a protective film on a substrate is very important in a semiconductor manufacturing process, such as manufacture of a liquid crystal device and manufacture of an optical device. A semiconductor manufacturing process is performed under a strict and accurate controlled circumstance, for example, acid or basic condition when soaking a surface of a substrate in solution, high temperature produced partially when sputtering to form a wiring electrode film on a substrate, and thus it is necessary to form a protective film on a surface of the device or a surface of a film. Nowadays, the protective film usually includes photosensitive insulated resin material and is formed by coating, light exposing, and developing process.
The protective film requires proper surface hardness, flat and smooth texture, and adhesion property to a substrate in order to protect underlying material under a severe condition during manufacturing processes. Moreover, it is more important that a protective film must have good properties of heat resistance, solvent resistance, insulativity, mechanical characteristics, and so forth. However, a surface of an underlying substrate is usually uneven and non-planar. As shown in FIG. 1, the protective film 12 does not completely cover a surface of an element 10 because of flowability of liquid protective film 12 before curing. A oblique portion F1, a corner of the oblique portion F1 and a flat portion F2, and other portions with large elevating angle cannot be completely covered by the protective film 12, and thus it leads to damages to the material underlying during the manufacturing processes and cause qualities and efficiency worse due to the uneven thickness and incomplete coverage of the protective film 12. An uneven thickness (Δt) and incomplete coverage of the protective film 12 can be produced based on different elevating angles of oblique portions and difference turning angles of a corner. Because of an oblique portion F1 with a larger elevating angle and/or a partial surface with a sharper turning angle, a more uneven protective film 12 can be formed.
Therefore, how to solve the abovementioned problems in order to provide a protective film with good properties of heat resistance, solvent resistance, insulativity, and coating uniformity and also resulting in good pattern resolution and complete cover on a surface of a protected element/film becomes the subject of the present invention.